This invention relates to a lubricant pressure compensator for a rotary earth boring tool.
Various lubricant relief valves for rock bits have been proposed to supply the lubricant to rotary portions of the bits. Examples are disclosed in U.S. Pat. Nos. 3,476,195 and 4,055,225, in which are disclosed flexible pressure compensators. However, these conventional compensators are not constructed of rigid and easily assembled parts. The present invention provides a novel structure of a lubricant pressure compensator in which rigid and easily assembled parts, that is, upper and lower capsule halves and a diaphragm member, are inserted into the lubrication reservoir to form a substantially spherical space so as to achieve an efficient and sensitive action of the movable member within a tough and strong compensator.